Rifle barrel with two sets of grooves of different depth and twist



MUSSER 2,967,369 H TWO SETS oF GROOVES OF DIFFERENT DEPTH AND TWIST Jan. 10, 1961 c RIFLE BARREL 2 Sheets-Sheet 1 Filed Jan. 13, 1960 a S S mu mm m m W C ATTORNEY:

Jan. 10, 1961 c w. MUSSER RIFLE BARREL WITH TWO SETS OF GROOVES OF DIFFERENT DEPTH AND TWIST 2 Sheets-Sheet 2 Filed Jan. 15, 1960 INVENTOR. G- WALTON MUSSER United States Patent RIFLE BARREL WITH TWO SETS OF GROOVES OF DIFFERENT DEPTH AND TWIST C Walton Musser, Beverly, Mass., assignor to the United States of America as represented by the Secretary of the Army Filed Jan. 13, 1960, Ser. No. 2,312

2 Claims. (CI. 42-78) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to rifles designed to fire difierent types of ammunition and more especially to an improved rifle which is operable to fire either a spin-stabilized projectile or a fin-stabilized projectile.

As is well understood by those skilled in the art, a projectile is said to be spin-stabilized when it is rotated at a speed sufiiciently high to prevent its tumbling. Such rotational speed is somewhat dependent on the size and configuration of the projectile and may be of the order of one thousand revolutions per second. It is produced by a rotating band which is fixed to the projectile and cooperates with the rifling of the gun to impart a twist to the projectile.

A fin-stabilized projectile is one which has fins attached to the rear of its boom. It is usually considered desirable to give it just enough spin to compensate for any off-center aerodynamic effects inadvertently produced in its manufacture. The rate of spin required to produce this result is much lower than that required to spin stabilize a projectile. Spin rates of 5 to revolutions per second are usually used. Rates in excess of this can efiect the stability as well as produce a marked reduction of penetration.

For this reason, it has not been possible heretofore to satisfactorily fire a spin-stabilized and a fin-stabilized projectile in the same gun.

In accordance with the present invention, this difiiculty is avoided and both spin rates can be positively obtained by the provision of a gun having difierent sets of rifiing, the first of which is adapted for use with spin-stabilized projectiles and the second of which is inscribed on the lands of the first rifling and is adapted for use with finstabilized projectiles. As hereinafter explained, the first rifling is relatively deep and has a relatively high rate of twist while the second rifiing is more shallow and twists at a much lower rate.

The invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope is indicated by the appended claims.

Referring to the drawings:

Fig. 1 is taken from a photograph looking into the rifle barrel from the breech end,

Fig. 2 is a developed view of the interior of the rifle barrel,

Fig. 2A is a section taken on the line 2A--2A of Fig. 2 and illustrating certain details of the rifling, and

Figs. 3 and 4 illustrate a tin-stabilized projectile adapted for use with the gun illustrated by the previous figures.

As can be seen from Fig. 1, the gun includes a barrel which has a relatively deep set of grooves 11 separated by lands 12. Superimposed on the lands 12 is a more shallow set of grooves 13 which are separated by lands 14.

The relation between these lands and grooves will be better understood from Figs. 2 and 2A. Here, there are shown 36 grooves 11, having one turn in 20 caliber and 78 grooves 13, having one turn in 360 caliber. Both sets of grooves have a right hand twist. The rifling 11-12 may have a bore diameter of 4.134 inches and a groove diameter of 4.208 inches. The rifling 13--14 may have a bore or lead diameter of 4.134 inches and a groove diameter of 4.146 inches. While these dimensions have been found to be satisfactory, it should be understood that the advantages of the invention are not limited thereto.

The vertical lines B, C and D are for the purpose of indicating the number of grooves 13 that would be tending to act as the projectile progressed between line B and line D. It is evident that at all points there would be approximately one-half of the 78 grooves tending to rotate the projectile, or approximately the same number of grooves as are active in the deep rifiing.

In the use of the gun, the deep rifling cooperates with a preengraved spin-compensated projectile in a conventional manner, the rotating band on the projectile being preengraved so that it engages the grooves 11 to approximately their full depth. Obviously the rotating band is unaffected by the shallow grooves 13.

When the riding is to be used with a tin-stabilized projectile, the projectile may be of the form illustrated by Figs. 3 and 4. Thus instead of a rotating band, there is provided a tapered seat 15 on which is a plastic band 16, the arrangement being such that the outside diameter of the band is no larger than the bourrelet of the projectile before the projectile is fired. When the projectile is fired, however, the band 16 is moved to the position indicated in Fig. 4 by the gas pressure resulting from the explosion. In this position it engages the grooves 13 and imparts a spin to the projectile. Another method of accomplishing the same result is to put a heavy coat of lacquer coating on the outside of the projectile. This coating should be thick enough to engage the grooves 13 but should not extend beyond the depth of these grooves.

I claim:

1. In a rifle barrel for firing different types of projectiles, the combination of means forming a first set of grooves having a predetermined depth and twist, and means forming a second set of grooves having a depth and twist substantially less than the depth and twist of said first set of grooves, said second set of grooves being inscribed on the lands between said first set of grooves.

2. A rifle barrel according to claim 1 wherein said first set of grooves has a twist designed to spin a projectile at a speed of the order of 1000 revolutions per second and said second set of grooves has a twist designed to spin a projectile at a speed of the order of 3 1000 revolutions per second.

References Cited in the file of this patent UNITED STATES PATENTS 

